Biologically active silicon dioxide (silica)-based glasses and glass-ceramics are known to the art. These materials are characterized by their ability to form a direct chemical bond of excellent strength with bone in vivo. The bond strength is not strongly dependent upon the degree of crystallinity of the biologically active material. However, the use of a partially or fully crystallized glass-ceramic is often preferred because devitrification increases the strength of the biologically active material itself. It has been proposed to construct a variety of dental and surgical implants for cement-free implantation from these biologically active glasses and glass-ceramics and of stronger materials such as aluminum oxide and surgical implant alloys coated therewith. The silica-based biologically active glasses and glass-ceramics of the prior art generally contain about 40 to 60 weight percent silica as the network former plus substantial levels of soluble modifiers such as sodium oxide, potassium oxide, calcium oxide, magnesium oxide, phosphorus pentoxide, lithium oxide and calcium fluoride. Boron oxide may be substituted for some of the silicon dioxide. A particularly preferred composition of the prior art, designated as composition 45S5, contains 45 weight percent silicon dioxide, 24.5 weight percent sodium oxide, 24.5 weight percent calcium oxide, and 6 weight percent phosphorus pentoxide. The chemical bond between a biologically active glass or glass-ceramic material and bone is to be distinguished from the mechanical type of bond formed by the ingrowth and interlocking of bone tissue within a macroscopically porous implant surface. Until now, it has been generally believed that a biologically active glass or glass-ceramic material possesses its activity because of its surface reactivity in physiological solutions. That is, soluble ions such as the sodium and calcium ions are selectively leached from the glass or glass-ceramic material, thereby causing the surrounding physiological fluid to become more alkaline. The alkaline solution then attacks the glass or glass-ceramic material, forming a silica gel layer thereon. It is to this silica gel layer, according to this proposed mechanism, that the fresh growing bone bonds [Hench, L. L., Splinter, R. J., Allen, W. C. and Greenlee, T. K., J. Biomed. Mater. Res. Symp., No. 2 (Part I), pp. 117-141 (1971); Hench, L. L. and Paschall, H. A., J. Biomed. Mater. Res. Symp., No. 4, pp. 25-42 (1973); Hench, L. L. and Paschall, H. A., J. Biomed. Mater. Res. Symp., No. 5 (Part I), pp. 49-64 (1974); Piotrowski, G., Hench, L. L., Allen W. C. and Miller, G. J., J. Biomed. Mater. Res. Symp., No. 6, pp. 47-61 (1975); Clark, A. E., Hench, L. L. and Paschall, H. A., J. Biomed. Mater. Res., 10, pp. 161-174 (1976); U.S. Pat. Nos. 3,919,723; 3,922,155; 3,981,736; 3,987,499; 4,031,571].
It is of course known to achieve the fixation of dental or surgical implants to the bone of the recipient by utilizing organic resin cements such as polymethylmethacrylate. However, there are known disadvantages in the use of such cements related to reactivity in vivo, toxicity, and loosening of the fixation. It is also known to strengthen an implant resin cement by incorporating therein various types of reinforcing material including particles of glass (see e.g. U.S. Pat. No. 3,919,773). Glass reinforced hardened inorganic cements (e.g. Portland cement) are also known (see U.S. Pat. No. 3,147,127).